Biological Invasion of Medically Important Bladder Snail Physella acuta Draparnaud, 1805 (Gastropoda, Physidae) in the Freshwater Habitat of Kerala, India

The acute bladder snail, Physella acuta (Draparnaud 1805) is globally considered as a highly invasive snail and it is synonymised to Physa acuta. This species is host to many trematodes causing foodborne diseases in humans. In the present study, P. acuta is recorded for the first time from Kerala state with its first mitochondrial DNA cytochrome c oxidase subunit I gene sequence from India. Twenty-three live specimens of P. acuta were collected from the Edappally Canal in Kochi, Kerala, India using a standard scoop net. The species was identified by morphological studies and confirmed using the barcoding technique. The snail was found attached to invasive freshwater plant Ceratophyllum demersum and other gastropod species Indoplanorbis exustus and Racesina luteola. The density of P. acuta was recorded as 25 ± 10 individuals per 50 cm long shoot. The shell length of the snail ranged between 3.2 and 7 mm, shell width 2–4 mm, aperture length 2.4–5.2 mm, aperture width 1–2 mm, and spire height 0.9–1.8 mm. The dead vacant shell has brownish yellow in colour while the live individuals were translucent having golden yellowish colour. The nucleotide BLAST results showed 100% similarity with the P. acuta sequences reported from Iraq. The specimen also showed a close match with the mtDNA COI sequence from Singapore, Thailand, Southeast Europe, France, Chile and the United States. The introduction of the snail to India is mainly through the aquarium trade. Their rapid growth rate, air-breathing capabilities and pollution tolerance make them a potential competitor to the native fauna. Besides, they could act as mediators of foodborne diseases in this southern state of the country.